1. Field of the Invention
This application relates to drilling and casing of earthen boreholes. Specifically, this application relates to a wear band for a tubular and a method of coupling a wear band to a tubular to be run into an earthen borehole. More specifically, this application relates to a friction-reducing wear band.
2. Brief Description of the Related Art
Earthen boreholes may be drilled using a tubular string, e.g., a drill string, to rotate a drill bit against the end of a borehole to remove material and extend the borehole. A drill string includes threadably connected segments of drill pipe that are typically rotated and longitudinally advance the drill bit into the earth's crust. Other drill strings may be coupled to a mud motor powered by pressurized fluid to rotate the drill bit as the drill string slides longitudinally along the borehole.
After a targeted depth is achieved, typically the drill string is removed from the borehole and a second type of tubular string called casing is made-up and run into the borehole to a targeted interval where it is cemented in place to stabilize the borehole. After a section of a borehole is cemented with casing, continued drilling through the bore of the cemented casing may further extend the borehole, and subsequent casing strings may be installed through the cemented sections of casing and cemented within the extended portion of the borehole to further stabilize and extend the borehole in a step-wise manner.
In extended reach boreholes and boreholes having horizontal or highly deviated sections, the frictional resistance to both rotational and longitudinal movement of a tubular is substantially greater because the weight of the tubular bears more directly on the floor (e.g., downwardly disposed side) of the borehole. There is a potential for damage or erosion of the outer surface of the tubular where the tubular is moved within the bore of an installed casing string when there is direct metal-to-metal contact.
Advances in drilling technology enable some boreholes to be drilled and cased using a single tubular that serves as both the drill string and the casing string. In this process, known as “casing while drilling,” a tubular may be used to rotate a drill bit to extend the borehole, and the tubular is then cemented into place within the borehole. Casing while drilling eliminates the need to trip drill pipe into and out of the borehole to service the drill bit or to clear the borehole for installation of a casing string. When the borehole is drilled to its targeted subsurface objective, the drill bit at the end of the casing string may either be milled out or collapsed to permit retrieval to the surface through the bore of the casing string. Casing while drilling may provide a significant cost savings from reduced drilling time and by eliminating the need to provide and maintain a drill string on a rig, and it may also reduce the risk of borehole collapse. However, casing is generally larger than drill pipe, thereby resulting in more frictional contact with the borehole, and the need to rotate the casing within the borehole may exacerbate wear.
Wear bands have been proposed to protect tubular strings from excessive wear. One such wear band, disclosed in U.S. Pat. No. 7,124,825 to Slack, is installed on a tubular by radial deformation of both a wear band sleeve and the adjacent wall of the tubular to crimp and secure the wear band on the tubular.
Another wear band solution, disclosed by Male et al.'s U.S. Pat. No. 7,412,761, provides a mold coupled to a tubular and filled with a composite material that hardens or cures to form a wear band.
A similar wear pad disclosed in Calderoni et al.'s U.S. Pat. No. 7,195,730 uses plastic compounds injected into molds that, upon curing or hardening, form strips or pads that adhere to the exterior wall of the tubular.
A centralizer disclosed in Clark et al.'s U.S. Publication 20080210419 provides one or more friction-reducing sliders disposed within one or more annular recesses or grooves machined within a bore through the centralizer to reduce rotational torque transmitted between the centralizer and a tubular received through the bore. A shortcoming of Clark et al.'s centralizer is that the body appears to slide along the tubular until it, and not a friction-reducing slider, engages an external feature on the tubular exterior, such as a sleeve-type tubular connection, another centralizer or a stop collar, resulting in unwanted friction between the rotating centralizer and that external feature.
What is needed is a wear band to reduce wear on a tubular that can be installed in the field, for example, at a pipe rack or a pipe yard, in almost any climate and without the need for large machines or skilled operators. What is needed is a wear band that does not require large, expensive sections of tubular to be threadably coupled intermediate adjacent sections of the tubular, and a wear band that can be coupled to a conventional tubular as opposed to being disposed on a special tubular section that must be included within the tubular string. What is needed is a wear band without small rolling elements (e.g., spherical bearings) that are subjected to an extremely large number of cycles or that are incompatible with uneven or rough rolling surfaces. What is needed is a wear band that reduces frictional resistance to both longitudinal and rotational movement of a tubular within a borehole or within the bore of a casing.